Studies on the Acrosome. X. Differentiation of the Starfish Acrosome*

Abstract

The course of acrosomal differentiation observed during spermiogenesis in two starfishes shows that the central components of the mature acrosome are produced by Golgi activity. In the early spermatid, small Golgi‐derived vesicles enter the hydrated acrosomal mass and appear to contribute their membrane constituents to the acrosomal‐membrane precursor elements. A single lamella of smooth endoplasmic reticulum and fine‐fibrillar material associated with it surround the membraneprecursor complex. In a drastic reorganization by which the spermatid acquires antero‐posterior symmetry, the acrosome becomes embedded in the anterior part of the nucleus directly beneath the plasma membrane. All the other organelles congregate in the posterior cytoplasm; a thin layer of cytoplasm persists around the sides of the nucleus. During late spermiogenesis two additional acrosomal components become increasingly conspicuous. One is the layer of fine‐fibrillar material associated with the smooth endoplasmic reticular vesicles surrounding the Golgi‐derived elements. This material is finally pushed towards the center of the sperm head by a late accretion of fibrous product which appears to be synthesized throughout spermiogenesis by the ribosomes, and accumulates around the anterior part of the acrosome as the cytoplasmic matrix diminishes.

Ultrastructural Observations on the Spermatogenesis of the Brittle-Star Amphipholis Kochii Lutken (Echinodermata : Ophiuroidea)

“…In recent years, fine structural observations of the spermatogenesis of the echinoderms have been extensively made, and many attentions have been paid to the acrosome formation (Longo and Anderson, 1969;Dan and Shirakami, 1971;Atwood, 1974;Pladellorens and Subirana, 1975;Bickell et al, 1980). All the foregoing observations on the acrosome structure agree in that the acrosome of the echinoderms is circular in shape.…”

“…All the foregoing observations on the acrosome structure agree in that the acrosome of the echinoderms is circular in shape. As to the beginning of the acrosome formation with an appearance of the proacrosomal vesicle, variation is found in the classes of the Echinodermata; in the holothuroid the proacrosomal vesicle is initially recognized in the spermatogonium (Atwood, 1974;Pladellorens and Subirana, 1975), in the crinoid it is in the spermatocyte (Bickell et al, 1980), and in the echinoid and asteroid in the spermatid (Longo and Anderson, 1969;Dan and Shirakami, 1971). However, in the ophiuroid the beginning of the acrosome formation is unknown up to date.…”

Polymerization of actin. VI. The polarity of the actin filaments in the acrosomal process and how it might be determined.

“…The polarity of these filaments is the same as that of the filaments which make direct reveals that the filaments located in the center of the actomere also decorate (Figs. [2][3][4], showing the same polarity as the actin filaments that extend from the apical and basal surfaces of the actomere. Thus the filaments which comprise the actomere can be identified as actin filaments.…”

The polymerization of actin: II. how nonfilamentous actin becomes nonrandomly distributed in sperm: evidence for the association of this actin with membranes

“…As has been documented by many investigators beginning in the 1890's (3,6,23), this vacuole is formed by the coalescence of numerous small vesicles produced from the Golgi apparatus (see Fig. 7 a).…”

“…7 a) (6). Furthermore, the small Golgi-derived vesicles which fuse to form the acrosomal vacuole are generally found in association with, and in suitable micrographs, are seen fusing with only that surface of the vacuole which possesses the thinner or less dense membrane.…”